1. Field of the Invention
The present invention relates to an intraruminal device, and more particularly to an intraruminal device for dispensing a time release medicament to a ruminant animal.
2. Description of Related Art
Domestically raised ruminant animals (e.g. goats, sheep and cattle) are typically sold by weight; the market price of such animals is proportional to their weight when sold. Ruminants are grazing animals, and are often left in open grazing fields for the entire grazing season. It is desirable that ruminants graze continuously throughout the season to gain as much weight as possible so they will fetch a high market price.
Unfortunately, many grazing fields contain bacteria which can infect grazing animals causing them to lose weight. Such bacterial infections require treatment with an antibiotic to combat the infection and ensure animal health. Ruminants are also susceptible to other forms of illness which can adversely affect their health or weight, and which must be treated with medication. Finally, farmers often wish to administer growth promoters, such as hormones, vitamins, etc., to their herd.
Such medicaments often must be administered slowly or periodically over time. It is difficult and expensive to regularly retrieve grazing animals to administer medicaments. Therefore, devices have been developed that are inserted into the rumen of such animals to control the time release administration of a medicament. Such a device is inserted when needed, for example at the beginning of the grazing season, and remains inside the rumen until the animal is slaughtered.
Existing intraruminal devices comprise a plastic housing containing a medicament matrix. The matrix is pressed against a first end of the device by a metal compression spring. Through an opening at the first end, the medicament matrix is exposed to ruminal juices which dissolve the matrix, thereby dispensing the dispersed medicament. Such devices have been shown to be effective at time releasing medicaments into the rumen. However, the metal spring in these devices is a major disadvantage.
Ideally, intraruminal devices should be retrieved from animals prior to processing. However, given the sheer volume of animals slaughtered each year, it is impossible to ensure proper removal of a present intraruminal device from each. Consequently, some intraruminal devices invariably slip through the slaughterhouses where they are ground up and processed. Metal springs are therefore highly disadvantageous in intraruminal devices because they can damage slaughtering equipment. More importantly, the metal fragments produced pose a risk of injury to a person eating the resulting processed meat.
Other nonmetallic means of providing compressive force to expel a medicament from a medication delivery device are known; e.g., vapor pressure means as disclosed in U.S. Pat. No. 3,797,492, osmotic pressure means as disclosed in U.S. Pat. No. 5,456,679, and electrolytic means as disclosed in U.S. Pat. No. 5,318,557. However, disadvantages of these compressive means are expense and difficulty of reliably implementing them in a compact intraruminal device.
It is therefore desirable to provide an intraruminal device having a mechanically supplied compressive force to dispense a medicament matrix without introducing significant additional complexity or cost to the device. Such a device should have no metal parts that may interfere with slaughterhouse equipment or injure a human upon ingestion in cases where the device is accidentally not removed.